ABSTRACT In September 2017, hurricane Maria devastated Puerto Rico's physical and medical infrastructure. The effects of these events on drug-use related morbidity and mortality will be large. Opioid Agonist Treatment (OAT) has proven to be effective in lowering HIV/HCV transmission while also reducing overdose episodes, yet the influence of natural disasters on enrollment and adherence among people who inject drugs (PWID) is not well known. This R21 project allows for a post-disaster data collection with rural PWID living in four rural communities in Puerto Rico to document behavioral and structural factors affecting barriers and facilitators to OAT enrollment. In addition, this project will also describe participants' experiences coping with the aftermath of hurricane Maria and its impact on their ability or motivation to participate in OAT. Hurricanes and other natural disasters might create and/or reinforce existing barriers to OAT access and adherence. It is critical to understand this previously unexamined aspect of OAT participation and access among PWID in order to develop cost-effective strategies, limit barriers, and improve OAT retention using innovative models that incorporate the most recent developments in epidemiology, prevention, and treatment. Understanding the individual and structural obstacles to OAT participation after a natural disaster, will contribute to evidence based policies to improve future OAT access in disaster-impacted areas. This study will build upon considerable pre-hurricane data collection in the region as part of the Injection Risk Networks in Rural Puerto Rico project (R01DA037117). Prior findings from 356 active PWID in rural PR conducted between 2015-2017 (finished a few months before Maria struck) suggests that while most respondents participated at some point in OAT, only one in three had participated during the last year and one in six tried to enroll but faced barriers that prevented their enrollment. The data collection proposed here will allow for demographic, epidemiological, and mental health comparisons from before and after hurricane Maria, derived from a cohort of drug users in rural Puerto Rico living in Cidra, Comerio, Cayey and Aguas Buenas. In addition, we will conduct 40 ethnographic ?treatment trajectory? narratives with a sub-sample of the PWID enrolled in the study. These interviews will collect narratives that focus on the lives and needs of participants as they move in and out of OAT treatment. These methods will help document cultural and structural determinants of addiction treatment and will provide additional evidence of the effects of hurricane Maria on OAT access. The current project will also allow our team to create an integrated knowledge exchange with a Community Advisory Board, whose understanding of the situation on the ground in Puerto Rico is likely to reflect post-disaster ideas about the current system of medically assisted treatment for opiate addiction on the Island. Post-disaster data collection on treatment access, adherence, and outcomes has the potential to significantly enhance our overall research capacity in rural areas and provide state and federal agencies with important knowledge to plan for and respond to future disasters.